The need for higher speed in vehicle data connectivity is increasing. This rapid growth is a result of the demand to have collision avoidance systems, lane departure warning systems, automatic braking systems, adaptive cruise control systems, and pedestrian detection systems incorporated into vehicles to support advanced driver assistance systems (ADAS). ADAS is the first step towards the larger goal of autonomous driving systems.
ADAS relies on many high resolution sensors that convey information to a central control module which compiles the data and decides how to best react to the situation. Due to the large amount of information (data) to be transferred from each high resolution sensor to the control module, data connectivity within the vehicle must be able to transfer the data quickly and reliably. The data connectivity must also be secure, in order to protect the information within the vehicle from outside attack and disruptions by individuals intent on causing malfunctions and damage to the vehicle.
As the ADAS systems within the vehicle become more complex and take responsibility for more control of the vehicle, higher data rates and bandwidth will be required driving the need for more complex data transmission lines.
The most popular form of data transmission line used for in-vehicle data connectivity today and the foreseeable future are cable pairs using differential signaling methods. Unshielded twisted pair (UTP) cables are the most commonly used differential pair cables due to their cost advantage and ability to reliably deliver data between two or more electronic devices. UTP cables are acceptable for lower data rate technologies in the 10 to 20 megabits per second (Mbps) range having a bandwidth in the 5 to 30 megahertz (MHz) range.
Twisted pair (TP) data cables have the unique feature that each line in the pair is intimately interacting electromagnetically with the other line of the pair. This electromagnetic (EM) interaction is not contained to just between the two lines 12,14 in the TP cable, but is about them in a cloud like form E as illustrated in FIG. 1. More detailed depictions of the individual electrical field (e-fields) and magnetic fields (h-fields) are available and are well known to those skilled in the art. FIG. 1 is a simple illustration of the basic concept.
As data rates increase, the containment of the EM cloud becomes even more important. At higher data rates, the use of an insulative jacket 18 surrounding the twisted pair 12, 14 as shown in FIG. 2 is recommended. The jacket 18 is primarily designed to maintain the geometry of the differential pair thereby providing more consistent mutual capacitance between the twisted pair over the length of the cable. This type of cable is commonly referred to as jacketed unshielded twisted pair (J-UTP) cable 10. J-UTP cable 10 is acceptable for certain data transmission protocols usually in the range of 20 to 100 Mbps having a bandwidth in the 30 to 150 MHz range. Jacketing of the cable adds cost to the finished cable.
As illustrated in FIG. 3, if the EM cloud E about the twisted pair 1, 2 is not contained within the jacket 18, interaction of the EM cloud E with the environment surrounding the cable may be induced and can cause signal integrity degradation due to impedance changes and other effects. In addition, data security is also impaired as others could intercept fluctuations in the EM cloud and capture the data that is being transmitted by the TP cable.
For data rates above 100 Mbps having a bandwidth greater than 150 MHz, a metal shield is used about the twisted pair and is known as shielded twisted pair (STP) cable. The STP cable is common in industry but requires that both ends of the shield are connected to an electrical ground. STP cable also requires the use of a shielded connector as the metal shield must contain every section of the TP cable. Since the shield is made of a continuous metal section, both ends must be properly grounded. If the metal shield is not properly grounded, the shield will act as an antenna potentially re-radiating the signals within shield or picking up EMI and coupling the interference to the conductors within the shield. The addition of the shield to the cable and the addition of metal sections to connected componentry drives additional cost and complexity to the finished system.
Ethernet data transmission protocol is being adopted for data transmission in automotive applications. Early automotive systems adopting Ethernet protocol are running at a data rate of 100 Mbps and require data connectivity that supports a bandwidth of at least 100 MHz. As the systems within the vehicle become more complex and take over more control of the vehicle, higher data rates and bandwidth of the connectivity will be required. Investigation into data protocols transmitting at 1000 Mbps having a bandwidth greater than 700 MHz is underway. However, issues are arising regarding the ability to transfer data at this rate and bandwidth in a cost effective way. Complexity of the vehicle harness routing, bundling of cable, external electromagnetic interference (EMI), and signal integrity (SI) are further complicating efforts to produce data signal cables in a cost effective manner.
Parallel wire transmission lines can also be used for data transmission at these rates. Parallel wire transmission lines are often used to reduce manufacturing burden by eliminating the twisting process, but they may not provide enough protection from electromagnetic interference (EMI) and typically require shielding.
Therefore, a cost effective, automotive data signal cable that is capable of transferring data at rates above 100 Mbps having a bandwidth of at least 100 MHz remains desired. The cable must maintain the ability to protect against EMI, and be able to be bundled and routed within a cable harness without affecting signal integrity.
The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also be inventions.